RIV entered into the BVTC (the exchange company that handles the trades) with specific terms that allows only those points purchases prior to 2019 and those points purchased directly from DVD as eligible to be converted from home resort points to
DVC vacation points to use at its resorts. In exchange for that, all RIV points bought on the resale market lose their ability to stay at the other resorts.
So, each set of resale points is restricted in some way, with only those direct points being purchased being equal in terms of trades. Currently, there are still 14 points that can't go into RIV resale, and only RIV resale that cant trade into the other ones...but at some point, that balance will shift when its no longer 14 resorts...in 2042...when it reduces to 9.
DVCMC is the one that takes care of home resort rules but BVTC can make their own rules for trading into the other resorts. For example, they could decide to make a different chart at VGF for non resort owners than they have for owners so that the exchange is not 1:1. They can charge a fee to trade into other resorts...it does not need to remain free. So, they have a lot of leeway in the rules. It doesn't even need to be the same for each DVC resort.
There is a clause in the BVTC document that states new resorts would be substantially similar...so some feel that RIV should not have been allowed to enter differently...however, with the grandfathering of everyone prior to that date, those who bought prior have the same trading rights as they did before. And, it is substantially similar for those with directly owned points. BVTC though has the right to amend the agreement as well, so that also gives them some leeway in the terms.
Now, there are some who don't agree that RIV should have been allowed....personally, I am not one of them...but, it has also never been challenged legally, so who knows how it would fair.
Trading, though, because resorts are not the same size, will never be equal. Prior to the new rooms, VGF has 2 million points and Poly had over 4 million, yet the trades were equal.